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Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, AB, Canada T1J 4B1
Corresponding author (acharya{at}em.agr.ca)
‘AC Oxley II’ cicer milkvetch (Reg. no. CV-193, PI 615074) (Astragalus cicer L.) was developed by the Agriculture and Agri-Food Canada Research Centre, Lethbridge, AB.
AC Oxley II, tested as LRC95-93-1, is a synthetic cicer milkvetch cultivar developed for improved seedling vigor and forage yield. About 5000 scarified seeds of Oxley cicer milkvetch cultivar were seeded in deep flats in the greenhouse in winter 1989. About 200 seedlings that emerged from a depth of 10 cm of a soil-free Cornell mix were transplanted to a poly-cross field nursery in summer 1990. In 1991, individual plants were scored for spring growth, ability to maintain growth during summer, and ability to produce seed. Plants showing poor growth were eliminated from the nursery before flowering. Fifty-four plants with improved agronomic performance were selected and the remaining plants were eliminated from the nursery. In the following winter (1991–1992), harvested seeds of these 54 selected plants (progeny rows) were scarified and tested for seedling vigor in deep flats. Seed was again harvested (1992) from the same 54 plants and were then tested for seedling vigor during the winter (1992–1993). The 38 most vigorous emerging plants from the 10 best progeny rows were transplanted to a poly-cross field nursery in summer 1993. Each plant was then vegetatively cloned into three and planted at random in the same nursery. Seed of each plant was collected separately in 1994 and 1995. Equal amounts of seed from each of the plants were bulked and the resulting population was designated as LRC95-93-1. Breeder seed plots for this synthetic were seeded in 1996 and 1999.
AC Oxley II is a perennial, rhizomatous, shallow rooted legume with indeterminate and prostrate growth habit. It has soft, hollow stems and pinnately-compound leaves with 19–25 leaflets. Seedling growth and regrowth after cutting of AC Oxley II is faster than those of Oxley. As is observed for other cicer milkvetch cultivars, AC Oxley II has better winterhardiness than any forage legume cultivar grown in western Canada. Forage stands show no susceptibility to diseases, while seed stands may show susceptibility to sclerotinia white mold [caused by Sclerotinia sclerotiorum (Lib.) de Bary]. Its white to pale yellow flowers are borne on racemes. Flowering occurs over a long period of time; some plants bloom from June to the first frost. At maturity, the black round leathery seed pods contain 3 to 11 bright yellow shiny seeds. AC Oxley II has larger seeds, 4.34 g 1000-1 seeds compared with 3.83 g for Oxley. Seeds do not shatter from the pods even after complete maturity.
AC Oxley II cicer milkvetch is intended for use as a pasture and silage legume in pure and mixed stands. It can produce a good hay crop in mixed stand with grasses. It produces more biomass than Oxley in dark brown (136% of Oxley), gray luvisol (120% of Oxley) and black soil (132% of Oxley) zones of western Canada. In brown soil zone AC Oxley II produced as much biomass as Oxley. This cultivar yielded 123 and 111% of Oxley check under dryland and irrigated conditions in western Canada, respectively. The mean total annual dry matter yield of this cultivar under irrigated conditions over 8 location-years was 8.74 t ha-1, whereas under dryland conditions over (26 location-years) it produced 5.4 t ha-1. Due to its winterhardiness and wide adaptation, the productive stand life of this cultivar is expected to be long (over 10 years).
AC Oxley II, like other cicer milkvetch cultivars, produces seed through cross pollination. Three species of indigenous bumble bees (Bombus huntii Green or B. nevadensis Cresson or to a lesser degree B. rufocinctus Cresson) are the main pollinators for this crop, although honey bees (Apis mellifera L.) and leaf cutter bees (Megachile rotundata Fibricius) have been found to improve seed set. The seed crop has to be either desiccated or swathed and allowed to thoroughly dry before seed combining. A high cylinder speed is required during threshing. AC Oxley II is a good seed producer and has produced, on average, about 500 kg ha-1 at Lethbridge under irrigation. This is about 10% better than Oxley seed yield. AC Oxley II has a high percentage of hard seeds and so needs to be scarified before planting. Both forage and seed stands of this cultivar should be planted with inoculated seeds using a special Astragalus bacterial inoculant. This cultivar establishes well when seeds are drilled 1.5 to 2 cm deep into a weed-free firm seed bed.
Breeder seed of AC Oxley II cicer milkvetch will be maintained by Agriculture and Agri-Food Canada Research Centre, Lethbridge, AB. Seed distribution rights have been granted to Prairie Seeds Inc., 1805 - 8th Street, Nisku, AB, Canada T9E 7S8 and Newfield Seeds Company Ltd., 701 Railway, Nipawin, SK, Canada S0E 1E0. Seed of AC Oxley II cicer milkvetch will be available for commercial production in 2002.
ACKNOWLEDGMENTS
I am grateful for the cooperation of individuals associated with the Western Forage Tests and the technical assistance of R.E. Dalton, D.R. Friebel and numerous summer students and members of the field crew.
NOTES
Accepted for publication May 31, 2001.
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